This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Transcription is a complex process that involves fine coordination between RNA Polymerase (RNAP) and various transcription factors. Being the first step of gene expression it is also the target for a wide variety of regulatory processes. Transcriptional pausing plays a central role and is a conserved mechanism in pro- and eukaryotes. It is involved in the regulation of gene expression and believed to be a prerequisite for termination of transcription in bacteria.Elongating RNAP can be stabilized in a paused state in vitro using well-characterized nucleic acid scaffolds. Transcription factors that are involved in pausing and termination, such as bacterial NusA can be added to study their mechanism. This provides a way to form well-behaved complexes for structural studies.